Generally, the widely-used peripheral input device of a computer system includes for example a mouse device, a keyboard device, a trackball device, or the like. Via the keyboard device, characters or symbols can be directly inputted into the computer system. As a consequence, most users and most manufacturers of input devices pay much attention to the development of keyboard devices.
Hereinafter, a key structure with a scissors-type connecting element in a conventional keyboard will be illustrated with reference to FIG. 1. FIG. 1 is a schematic side cross-sectional view illustrating a conventional key structure. As shown in FIG. 1, the conventional key structure 1 comprises a keycap 11, a scissors-type connecting element 12, a rubbery elastomer 13, a membrane switch circuit member 14 and a base plate 15. The keycap 11, the scissors-type connecting element 12, the rubbery elastomer 13 and the membrane switch circuit member 14 are supported by the base plate 15. The scissors-type connecting element 12 is used for connecting the base plate 15 and the keycap 11.
The scissors-type connecting element 12 is arranged between the base plate 15 and the keycap 11, and the base plate 15 and the keycap 11 are connected with each other through the scissors-type connecting element 12. The scissors-type connecting element 12 comprises a first frame 121 and a second frame 122. A first end of the first frame 121 is connected with the keycap 11. A second end of the first frame 121 is connected with the base plate 15. The rubbery elastomer 13 is enclosed by the scissors-type connecting element 12. The membrane switch circuit member 14 comprises plural key intersections (not shown). When one of the plural key intersections is triggered, a corresponding key signal is generated. The rubbery elastomer 13 is disposed on the membrane switch circuit member 14. Each rubbery elastomer 13 is aligned with a corresponding key intersection. When the rubbery elastomer 13 is depressed, the rubbery elastomer 13 is subjected to deformation to push the corresponding key intersection of the membrane switch circuit member 14. Consequently, the corresponding key signal is generated.
The operations of the conventional key structure 1 in response to the depressing action of the user will be illustrated as follows. Please refer to FIG. 1 again. When the keycap 11 is depressed, the keycap 11 is moved downwardly to push the scissors-type connecting element 12 in response to the depressing force. As the keycap 11 is moved downwardly relative to the base plate 15, the keycap 11 pushes the corresponding rubbery elastomer 13. At the same time, the rubbery elastomer 13 is subjected to deformation to push the membrane switch circuit member 14 and trigger the corresponding key intersection of the membrane switch circuit member 14. Consequently, the membrane switch circuit member 14 generates a corresponding key signal. When the keycap 11 is no longer depressed by the user, no external force is applied to the keycap 11 and the rubbery elastomer 13 is no longer pushed by the keycap 11. In response to the elasticity of the rubbery elastomer 13, the rubbery elastomer 13 is restored to its original shape to provide an upward elastic restoring force. Consequently, the keycap 11 is returned to its original position where it is not depressed.
Generally, if the foreign liquid is introduced into the key structure, the membrane switch circuit member is possibly in a short-circuited state. For solving this problem, the membrane switch circuit member is designed to be a sealed structure with a waterproof function. Since the inner space of the sealed membrane switch circuit member contains gas, the inner gas is subjected to expansion or contraction in response to the temperature change. When the temperature increases, the volume of the inner gas expands. Consequently, it is difficult to make electric conduction of the key intersection of the membrane switch circuit member. When the temperature decreases, the volume of the inner gas contracts. Meanwhile, it is easy to make electric conduction of the key intersection of the membrane switch circuit member. However, the keyboard device is possibly suffered from an error operation. For easing the electric conduction of the membrane switch circuit member, the membrane switch circuit member membrane switch circuit member is equipped with a gas-escaping channel to escape the gas from the membrane switch circuit member. Due to the arrangement of the gas-escaping channel, the membrane switch circuit member is not the sealed structure. Under this circumstance, the waterproof efficacy is deteriorated.
Therefore, there is a need of providing a keyboard device with a waterproof function and capable of avoiding error operation.